1. Field of the Invention
The present invention relates to an IC card, an IC card processor, and an IC card system. The present invention can be applied to an IC card having various sorts of data input thereto or output therefrom in a non-contact manner, to an IC card processor which performs data communication with the IC card, and to an IC card system using the IC card.
2. Description of the Related Art
IC card systems using IC cards have been applied to ticket examination systems for use in transport facilities, room entry/exit control systems, etc. An IC card system of this kind has been proposed which is constituted of IC cards carried by users and a read/writer (i.e., IC card processor) for exchanging various sorts of data with each of the IC cards. Various sorts of data are transmitted and received between the IC card and the read/writer in a non-contact manner.
That is, in this kind of IC card system, the read/writer forms a transmission signal by modulating a carrier having a predetermined frequency with a desired data sequence, and sends out the transmission signal to the IC card via an antenna.
The IC card receives the transmission signal via an antenna and demodulates the transmission signal to extract the data sent from the read/writer. Further, the IC card sends out data such as personal information stored therein to the read/writer in response to the received data by modulating a predetermined carrier with the data to be transmitted.
The read/writer receives the data sent from the IC card, and opens or closes a door of a ticket examination machine or allows entry into or exit from a room.
Data exchange between the IC card and the read/writer may be executed based on a full-duplex method to reduce the time required for data exchange and to improve the handling of this kind of IC card system.
To enable data exchange based on a full-duplex method, the carrier frequency of the transmission signal to be sent out from the read/writer and the carrier frequency of the response signal to be sent out from the IC card are set to different frequencies.
However, the problem of a reduction in the efficiency of use of the frequency band is then encountered.
It is also necessary to efficiently transmit and receive the transmission signal and the response signal having different frequencies. Therefore, there is also a problem of the construction of the antennas, etc., becoming complicated.
In the case of a type of IC card operating by electric power of a received transmission signal, it is necessary to receive electric power by efficiently receiving the transmission signal and to efficiently transmit data by low electric power. If the efficiency of transmission and reception of the transmission signal and the reception signal cannot be sufficiently increased, the operation of the IC card is unstable.
In view of the above-described problems, an object of the present invention to provide an IC card, an IC card processor and an IC card system arranged so as to be simple in configuration as well as to be capable of data exchange based on a full-duplex method effectively utilizing a frequency band.
To achieve the above-described object, according to one aspect of the present invention, there is provided an IC card in which a response signal is formed by modulating a main carrier having the same frequency as a main carrier of a transmission signal with a response data sequence corresponding to a transmitted data sequence in such a manner that its sideband does not overlap a sideband of the transmission signal along the frequency axis.
According to another aspect of the present invention, there is provided an IC card processor in which a transmission signal is formed by modulating a main carrier having the same frequency as a main carrier of a response signal with a transmitted data sequence urging sending out of the response data sequence in such a manner that its sideband does not overlap a sideband of the response signal along the frequency axis. The transmission signal is sent out from a predetermined antenna.
There is also provided an IC card system in which an IC card forms a response signal by modulating a main carrier having the same frequency as a main carrier of a transmission signal with a response data sequence corresponding to a transmitted data sequence in such a manner that its sideband does not overlap a sideband of the transmission signal along the frequency axis, the IC card sending out the response signal from an antenna.